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Bombelli's treatment

Raffaele Bombelli (1526-1573) took this concept even further by considering the cubic tex2html_wrap_inline220, which was known to have 4 as the only positive root. Nonetheless, Cardan's formula produced the solution tex2html_wrap_inline222. Bombelli considered the following identity: tex2html_wrap_inline224, which brought him to the conclusion that tex2html_wrap_inline226. Thus imaginary or fictitious numbers found some practical use.

Leo Liberti
Thu Feb 26 17:04:11 CET 1998